Devices for enabling patients to test their own blood are well known in the art. One such device is shown in U.S. Pat. No. 4,552,458, to Lowne, which deals with a compact reflectometer to enable the exposure of a reagent to different light beams, one red and one green. The light beams are folded by a reflecting surface, which redirects the beams through a transparent glass plate onto a reagent strip. Light is reflected back from the strip along a similar folded path onto a detector located in the same plane as the light sources.
Other patents describing various optical arrangements for illuminating and detecting the light reflected from reagent strips are U.S. Pat. No. 4,632,559, to Miles, for an optical read head for measuring non-specular, i.e. non-mirror-like, reflections from a reagent test strip; U.S. Pat. No. 4,787,398, to Garcia, for a glucose medical monitoring system and U.S. Pat. No. 4,985,205 for a test carrier analysis system.
The latter '205 patent describes a reference measurement using the same optical elements by using the same reference layer so as to avoid a two tier testing process. The reference measurement uses two LED's for illuminating the same color formation layer from different directions. The LED's are preferably activated successively so that the measurements can then be averaged.
U.S. Pat. No. 5,039,225 describes a device for measuring optical density with a light transmissive plate inserted between the light source and the surface being measured. The light is directed at an angle relative to a surface of the plate so that a portion is reflected back to a detector for obtaining a reference measurement while another detector is oriented to detect diffuse light for analysis.
Other patents related to body fluid analysis are U.S. Pat. Nos. 5,114,350; 5,279,294 for a glucose diagnostic device which can fit inside a shirt pocket; U.S. Pat. No. 5,321,492 using a dual function read head for a glucose level detector; U.S. Pat. No. 5,424,035 for a glucose test strip positioning structure; U.S. Pat. No. 5,424,545 for a non-invasive spectro-photometric technique to determine glucose levels; U.S. Pat. Nos. 5,518,689 and 5,611,999 for a diffused light reflectance technique wherein the reagent sample is held at a particular angle relative to the incident beam to obtain an improved performance; U.S. Pat. Nos. 5,563,042 and 5,597,532 for particular types of glucose test strips.
None of the these patents describe or disclose a small personally useable body fluid diagnostic instrument with which both glucose and fructosamine levels in a blood sample can be detected.